Temperature controlled process and chamber lid

ABSTRACT

The invention relates to an apparatus and process for the vaporization of liquid precursors and deposition of a film on a suitable substrate. Particularly contemplated is an apparatus and process for the deposition of a metal-oxide film, such as a barium, strontium, titanium oxide (BST) film, on a silicon wafer to make integrated circuit capacitors useful in high capacity dynamic memory modules.

This is a divisional application of U.S. patent application Ser. No.08/927,700 filed Sep. 11, 1997 pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus and process for the vaporizationof liquid precursors and deposition of a film on a suitable substrate.Particularly contemplated is an apparatus and process for the depositionof a metal-oxide film, such as a barium strontium titanate (BST) film,on a silicon wafer to make integrated circuit capacitors useful in highcapacity dynamic memory modules.

2. Background of the Invention

The increasing density of integrated circuits (ICs) is driving the needfor materials with high dielectric constants to be used in electricaldevices such as capacitors for forming 256 Mbit and 1 Gbit DRAMs.Capacitors containing high-dielectric-constant materials, such asorganometallic compounds, usually have much larger capacitance densitiesthan standard SiO₂ --Si₃ N₄ --SiO₂ stack capacitors making them thematerials of choice in IC fabrication.

One organometallic compound of increasing interest as a material for usein ultra large scale integrated (ULSI) DRAMs is BST due to its highcapacitance. Deposition techniques used in the past to deposit BSTinclude RF magnetron sputtering, laser ablation, sol-gel processing, andchemical vapor deposition (CVD) of metal organic materials.

A liquid source BST CVD process entails atomizing a compound, vaporizingthe atomized compound, depositing the vaporized compound on a heatedsubstrate and annealing the deposited film. This process requirescontrol over the liquid precursors and gases from introduction from anampoule into a liquid delivery system through vaporization andultimately to the surface of the substrate where it is deposited. Thegoal is to achieve a repeatable process which deposits a film of uniformthickness under the effects of a controlled temperature and pressureenvironment. The goal has not been satisfactorily achieved because theprecursors are finicky and the deposition equipment requires a complexdesign.

For example, one difficulty encountered is that the delivery of liquidprecursors has typically required positive displacement pumps. Pumps canbecome clogged and require replacement if the precursors deposit on thesurfaces of the pumping system. In addition, use of positivedisplacement pumps becomes problematic when the delivery lines or thevaporizer become clogged with deposits because the pump can rupture thepressure seals or continue to operate until the pressure relief valveson the pump are tripped. Either result may require maintenance andrepair and over time repair and replacement of pumps becomes veryexpensive and increases the cost of ownership of the equipment.

Another difficulty encountered is that BST precursors have a narrowrange of vaporization between decomposition at higher temperatures andcondensation at lower temperatures thereby requiring temperaturecontrolled flow paths from the vaporizer into the chamber and throughthe exhaust system. In addition, the liquid precursors tend to formdeposits in the delivery lines and valves disposed throughout thesystem.

Another difficulty encountered is the difficulty or lack of efficiencyin vaporizing the liquid precursors. Typically, only a portion of theliquid precursors are vaporized due to low conductance in the vaporizer,thereby inhibiting deposition rates and resulting in processes which arenot consistently repeatable. In addition, known vaporizers used in CVDprocesses incorporate narrow passages which eventually become cloggedduring use and are not adapted for continuous flow processes which canbe stabilized. This too results in a reduction in vaporizationefficiency of the liquid precursors and negatively affects processrepeatability and deposition rate. Still further, known vaporizers lacktemperature controlled surfaces and the ability to maintain liquidprecursors at a low temperature prior to injection into the vaporizer.This results in deposition of material in the injection lines in thevaporizer and premature condensation or unwanted decomposition of theprecursors.

Still another difficulty encountered in the deposition of BST is thatthe deposition process is performed at elevated substrate temperatures,preferably in the range of about 400-750° C. and the annealing processis performed at substrate temperatures in the range of about 550°-850°C. These high temperature requirements impose demands on the chambersused in the deposition process. For example, elastomeric O-rings aretypically used to seal the deposition chamber and are not generally madeof materials that will resist temperatures in excess of about 100° C.for many fabrication cycles. Seal failure may result in loss of properchamber pressure as well as contamination of the process chemistry andthe system components, thereby resulting in defective film formation onthe wafer. In addition, it is necessary to prevent temperaturefluctuations of system components which result from thermal conduction.Loss of heat due to thermal conduction causes temperature gradientsacross the surface of the substrate resulting in decreased uniformity infilm thickness and also increases the power demands required of thesystem to maintain the high temperature environment in the chamber.

There is a need, therefor, for a deposition apparatus and method whichcan deliver liquid precursors to a vaporizer, efficiently vaporize theprecursors, deliver the vaporized precursors to the surface of asubstrate and exhaust the system while maintaining elevated temperaturesin the chamber, preventing unwanted condensation or decomposition ofprecursors along the pathway and avoiding temperature gradients in thesystem. It would be preferable if the system were adapted for rapidcleaning and continuous flow operation.

SUMMARY OF THE INVENTION

In one aspect of the invention, a deposition chamber is provided fordepositing BST and other materials which require vaporization,especially low volatility precursors which are transported as a liquidto a vaporizer to be converted to vapor phase and which must betransported at elevated temperatures to prevent unwanted condensation onchamber components. Preferably, the internal surfaces of the chamber aremaintainable at a suitable temperature above ambient, e.g., 200-300° C.,to prevent decomposition and/or condensation of vaporized material onthe chamber and related gas flow surfaces. The chamber comprises aseries of heated temperature controlled internal liners which areconfigured for rapid removal, cleaning and/or replacement and preferablyare made of a material having a thermal coefficient of expansion closeto that of the deposition material. The chamber also preferably includesfeatures that protect chamber seals, e.g., elastomeric O-rings, from thedeleterious effects of high temperatures generated during fabrication ofelectrical devices, such as capacitors useful for ULSI DRAMs. Thisconcept is generally referred to as a "hot reactor" within a "coolreactor".

The invention also provides a vaporizing apparatus having large vaporpassageways for high conductance to prevent clogging for consistentlymixing and efficiently vaporizing liquid precursor components, anddelivering the vaporized material to the deposition chamber withnegligible decomposition and condensation of the gas in the vaporizerand gas delivery lines. Preferably, the apparatus increases vaporizingefficiency by providing increased surface area and a tortuous pathwaywith wide passages to reduce the likelihood of fouling or cloggingtypically associated with existing vaporizers.

The invention also provides a system for delivering liquid sourcecomponents to the vaporizer without requiring high pressure pumps andwhich provides gravity assisted feed and cleaning of the lines.Pressurized ampoules deliver the liquid precursors into the vaporizer.The ampules are preferably chargeable up to about 500 psi using an inertgas such as argon. The use of pressurized ampoules eliminates the needfor high pressure pumps to deliver the liquid precursors into thevaporizer.

The invention also provides a liquid and gas plumbing system whichallows access into the chamber without requiring that any hard plumbinglines be disrupted. Preferably, vaporized materials are delivered fromthe vaporizer through the chamber body and into a gas distributionassembly in the lid which includes a mixing gas manifold and a gasdistribution plate. The chamber body and the mixing gas manifold of thelid sealably connect gas passages disposed therein on engagement.

Still further, the invention provides a flushable system which canoperate in a continuous flow mode or a discontinuous mode where it isturned off during the transfer of substrates into or out of the chamber.One or more zero dead volume valves and a gravity feed system enable thesystem to cycle between a deposition mode where the liquid precursorsare vaporized and delivered to the chamber and a substrate transfer modewhere solvent is delivered to the lines and valves to flush the systemto prevent build-up of material in the liquid/vapor delivery lines. Thesolvent can be routed through the liquid delivery lines, the vaporizerand through a bypass line and into a disposal system. In addition, thesystem may continually vaporize precursors but deliver the vaporizedmaterial to the exhaust system through a bypass line. This enablesstabilization of the process over a number of substrates throughoptimization and maintenance of the vaporization process.

Still further, the invention provides a pumping system for the chamberwhich can maintain chamber pressures at a high vacuum state and whichhas a plumbing system configured to protect the pumps from deposition ofdeposits therein. In one aspect of the invention, cold traps aredisposed upstream from an exhaust pump to remove vaporized gas from thesystem. In another aspect of the invention, a high vacuum pump isselectively isolated from the exhaust passage by a suitable valve suchas a gate valve to enable selective communication with the high vacuumpump in the absence of process gases.

The chemical vapor deposition system of the present invention ischaracterized by its use in the manufacture of capacitor films ofconsistently high quality, with significantly reduced maintenance timesand easier maintenance and capability for depositing CVD films at highrates with less particle generation. The net result is a fabricationprocess with enhanced efficiency and economy.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a chamber system of the presentinvention;

FIG. 2 is cross sectional view of a chamber of the present invention;

FIG. 3a is a cross sectional view of a heated gas delivery line throughthe chamber wall;

FIG. 3b is a cross sectional view of a gas delivery line through thechamber wall;

FIG. 4 cross sectional view of an alternative embodiment of a chamberand associated purge gas pumping nose assembly of the present invention;

FIG. 5 is a substantially bottom perspective view of a chamber liner;

FIG. 6 is a cross sectional view of a chamber liner showing a connectorfor a resistive

FIG. 7 is a top view of a lid of the present invention;

FIG. 8 is a partial cross sectional view of a gas manifold;

FIG. 9 is a top view of a gas manifold;

FIG. 10 is a cross sectional view of a gas manifold;

FIG. 11 is a side view of a heated nose liner;

FIG. 12 is an end view of a mounting flange for the nose liner;

FIG. 13 is a perspective view of a cold trap filter member;

FIG. 14 is a perspective view of a chamber and vaporizer module;

FIG. 15 is a cross sectional view of a vaporizer of the presentinvention;

FIG. 16 is a top schematic view of a fin structure of the vaporizer ofthe present invention;

FIG. 17 is a cross sectional view of an alternative embodiment of avaporizer;

FIG. 18 is a schematic of a liquid delivery system;

FIG. 19 is a perspective view of a zero dead volume valve;

FIG. 20 is a cross sectional view of a zero dead volume valve; and

FIGS. 21-27 are graphical representations of characteristics of apreferred CVD BST 200 mm process.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a liquid delivery chemical vapordeposition (CVD) system useful in depositing thin metal-oxide films aswell as other films requiring vaporization of precursor liquids. Thesystem has particular application for the fabrication of metal-oxidedielectrics useful in making capacitors used in ULSI DRAMs as well as anumber of other electrical devices. In general, devices that can be madewith the present system are those characterized by having one or morelayers of insulating, dielectric or electrode material deposited on asubstrate.

FIG. 1 is a perspective view of a CVD system 10 of the presentinvention. The system 10 generally includes a chamber body 12, a heatedlid assembly 14, an integrated vaporizer module 16 and anexhaust/pumping system 18. Not shown in this figure, but a feature ofthe invention, is a liquid delivery system for supplying the liquidprecursors to the vaporizer module. The size and dimensions of thesystem are dictated by the size and shape of the workpiece on whichprocesses of the present invention are performed. A preferred embodimentof the invention will be described herein with reference to a chamberadapted to process a circular substrate, such as a 200 mm silicon wafer.

The inventors have recognized that deposition layer uniformity can beenhanced, and system maintenance can be reduced, if substantially all ofthe system components (other than the substrate and substrate heater)which "see" the process chemistry are substantially maintained at anideal isothermal system temperature (e.g., 250° C.±5° for BST). Thedeposition chamber incorporates several active and passive thermalcontrol systems, including features for minimizing temperature gradientsthat can be created as a result of the relatively high temperature ofthe substrate and the substrate support member. The deposition chamberalso includes thermal control features which serve to protect a mainchamber seal by cooling it below the ideal isothermal systemtemperature. Other similar thermal control features maintain a coverenclosing the chamber lid at a relatively safe temperature to preventburn injuries. Cooling is achieved without inducing significanttemperature fluctuations and gradients in the system components exposedto the system chemistry, and without excessive cooling and heating powerlosses.

The Deposition Chamber

FIG. 2 is a cross sectional view of one embodiment of a depositionchamber showing the chamber body 12 supporting a heated lid assembly 14.The chamber body 12 defines an inner annular processing region 20defined on the perimeter by an inner wall 22. A substrate support member24 extends through the bottom of the chamber and defines the lower endof the processing region 20. A gas distribution plate 26 mounted on thelid forms the upper limit of the processing region 20. The chamber body12 and the lid assembly 14 are preferably made of a rigid material suchas aluminum, stainless steel or combinations thereof. The chamber body12 also defines a pumping port for purging the remains of the depositionvapor once it has been delivered over the substrate. A generallyU-shaped passage surrounding the gas distribution assembly forms apumping channel through which gases are drawn into the exhaust system.

The substrate support member 24 may comprise a metal, e.g., aluminum,with a resistive heating element attached thereto or embedded therein.Alternatively, the support member may comprise a ceramic block andembedded ground plate which generates heat when subjected to RF energyemitted by an adjacent electrode. A suitable substrate support memberand related lift assembly is shown and described in co-pending U.S.patent application Ser. No. 08/892,612, entitled "Improved Self AligningLift Mechanism," filed on Jul. 14, 1997, and is incorporated herein byreference. This substrate support member is available from AppliedMaterials, Inc. of Santa Clara, Calif. under the model name CxZ Heater.

The substrate support member generally is movable up and down on acentral elevator shaft 30 to move a substrate between a depositionposition adjacent the gas distribution plate 26 and a substrateinsertion/removal position below a slit valve formed through the chamberbody. The entry point of the shaft into the chamber is sealed with acollapsible bellows (not shown). The substrate is lifted from or placedon a robot blade by a set of lifting pins 32 slidably retained in a setof four passageways 34 extending through the substrate support member24. Directly below each of the pins is a lifting plate 36 which movesthe pins vertically within the chamber to allow a substrate to be liftedoff or placed on a robot blade which is moved into the chamber throughthe slit valve opening (not shown).

The chamber body 12 defines one or more passages 38 for receiving aheated gas delivery feedthrough 40 having an inlet 42 and an outlet 44to deliver one or more precursor gases into the gas distribution plate26 mounted on the lid assembly 14. The passage 38 defines an upper and alower end of differing diameters to form a shoulder 58 where the upperand lower ends meet. The gas outlet 44 is fluidically connected to amixing gas manifold 46 which includes at least a first gas passage 48 todeliver a gas(es) into the gas distribution plate 26. An O-ring seal 50,preferably made of TEFLON® with a stainless steel c-spring, is locatedaround the outlet 44 on the upper chamber wall to provide a sealingconnection between the gas delivery feedthrough 40 and the gas manifold46.

FIG. 3a is a cross sectional view showing a heated gas deliveryfeedthrough 40 disposed in the annular passage 38 formed through thechamber wall. The passage includes a shoulder 58 disposed on the upperend of the passage and includes an O-ring seal 60. The feedthroughpreferably includes an outer conduit 41 and an inner conduit 45 disposedwithin the outer conduit. The outer conduit includes a mounting shoulder43 which is mounted on shoulder 58 of the passage. The outer conduitalso includes a lower end having threads thereon for receiving a locknut to secure the feedthrough in a sealing position within the passage38 against the shoulder 58 and O-ring seal 60. The inner conduit 45defines an upper mounting surface 49 for forming a seal with the lidassembly at O-ring seal 50 and also includes a flange 62 on its lowerend for mating with the bottom of the chamber body. A cable type heater64, or other suitable heater, is disposed in intimate contact with theinner conduit of the feedthrough to heat the feedthrough to a desiredtemperature. A radiation shield 65 is disposed over the heater toprevent thermal radiation from heating the outer conduit 41. A powerlead 67 extends from the lower end of the feedthrough and is connectedto a suitable power source to heat the feedthrough. A thermocouple 66 isinserted or otherwise disposed in the heated gas delivery feedthrough 40to monitor the temperature thereof. The feedthrough is mounted in thepassage and secured therein using a screw type connector or othersuitable connector.

The upper wall 47 of the outer conduit 41 is thinned and sized to definea gap between its outer surface and the inner wall of the chamber bodyto provide a heat choke adjacent the O-ring seal 60. O-ring seal 50 ispreferably a hot O-ring which can withstand temperatures of about 250°C. The thin wall minimizes heat conduction down to the shoulder 58 toprotect O-ring seal 60. By minimizing heat conduction, less power isrequired to heat the feedthrough. Additionally, less thermal massprovides better thermal control and faster response for the feedbackcontrol. Still further, the heat choke on the outer conduit preventsheat loss from the mixing gas manifold 46 which is directly connected tothe insert and which is heated by the lid body. This avoids generationof cold spots along the path of the vaporized gas.

FIG. 3b illustrates an embodiment of a gas feedthrough which is notheated. The oxidizer gas(es) are flown through this non-heatedfeedthrough. However, in applications where a heated oxidizer gasfeedthrough is required, one similar to that shown in FIG. 3a can beused. The feedthrough of FIG. 3b resembles that of FIG. 3a except thatthe cable heater and thermocouple are removed. In addition, the sizes ofthe feedthrough may vary depending on the requirements of the process.In one embodiment, the non-heated oxidizer gas feedthrough has a smallergas passage and the overall dimensions are therefor somewhat smaller.

FIG. 4 is a cross sectional view of an alternative embodiment of thepresent system. A deposition vapor inlet passageway 68 whichcommunicates directly with a vaporizer outlet port may extend axiallythrough the lid assembly 14. An annular recess surrounding the inletpassageway is formed on a top side of the main lid body.

Referring again to FIG. 2, removable deposition chamber liners (whichcan be used at a number of different locations) facilitate periodiccleaning of the deposition chamber. A liner in accordance with apreferred embodiment of the invention includes an integral orfunctionally integral (i.e., assembled from one or more components asattached or overlapping units) generally chamber liner 28 that coversupper chamber surfaces adjacent the substrate support member 24 and abottom liner 21 covers the lower chamber wall surfaces below substratesupport member. The liner material may be made of a metal, e.g.,stainless steel or aluminum, a ceramic material (e.g., Al₂ O₃) orquartz, and can be equipped with an active PID controlled heatingelement which maintains the liner walls substantially at the optimumisothermal system temperature to inhibit both condensation anddecomposition of gas vapor on the chamber surfaces. The material fromwhich the liner is made preferably demonstrates chemical resistance tohalogens and halogenated in situ cleaning compounds, and is preferablynot adversely affected by, nor adversely affects, the process chemistry.

Referring again to FIG. 2, a chamber liner 28 is preferably disposedadjacent the inner wall 22 of the chamber to provide a removable surfacewithin the chamber which can be easily cleaned and/or replaced. Theliner 28 is supported in the chamber on supports 23, preferably three,which are equally spaced around the lower surface of the liner. Thesupports 23 are sized to minimize the contact area between the chamberliner 28 and the chamber body and thereby minimize heat conductionbetween the liner and the chamber body. In one embodiment, the liner isheated by radiation from the heated lid and the heated substrate supportmember. This embodiment is referred to as a passive floating liner.Alternatively, the liner may also include a resistive heater 25 (shownin FIG. 5), or other suitable heater, disposed therein so that it can beactively heated and maintained at an ideal isothermal temperature. Thisactively heated embodiment is referred to as an active floating liner.FIG. 5 is a substantially bottom perspective view of a heated liner 28having a resistive heater 25 disposed therein and an electricalconnector 27 mounted on the lower surface of the liner which houses theelectrical connections to the coil.

FIG. 6 is a cross sectional view through the active floating liner 28showing an external housing mounted on the bottom of the chamber throughwhich the electrical connector 27 is disposed. Due to thermal expansionof the liner, accommodation of the expansion is preferably provided orresisted by the external housing mounted on the chamber. The externalhousing includes a first conduit 29 having a flange 31, 33 disposed oneach end thereof for mounting to the bottom of the chamber and formounting a bellows 35, respectively. The bellows is mounted on one endto the lower end of flange 33 and at the other end to a second conduit137 at a flange 39 provided therefor. The bellows is sized and adaptedto flex to accommodate any thermal expansion in the electrical connector27 or the liner 28. The electrical connections to the coil extendthrough the end of the second conduit 137 for easy connection to a powersource.

Since the portions of the liner below the substrate support member aretypically isolated from the vapor flow, temperature control of theseparts is less critical. However, the portion of the liner below thesubstrate support member may also be actively heated using a resistivetype heating element, or other suitable heating member. Preferably, thetemperature of the liner both above and below the substrate supportmember should be maintainable within the optimum isothermal systemtemperature range, e.g., between about 200° C. and 750° C., or othertemperature range suitable for the desired deposition material.

A sealing edge ring 160 (shown in FIG. 2) is disposed in the chamber andsupported on the substrate support member 24 to contact and overlap acircumferential edge of the substrate support member 24. Acircumferential rib can be provided on the underside of the ring inorder to maintain the ring in an aligned position. The edge ring servesto close-off the annular space 162 between the liner 28 and thesubstrate support member 24, and thereby substantially reduce the amountof deposition vapor which flows into the lower part of the depositionchamber. In addition, the edge ring acts as a radiation shield. Theouter circumferential portion of the gas distribution plate 26 typicallyextends beyond the diameter of the substrate. The edge ring 160 protectsthis part of the gas distribution plate 26 from heat directly radiatedby the substrate support member. The edge ring 160 is preferably made ofa material having a thermal coefficient of expansion similar to that ofthe deposition material to reduce the possibility of particle generationdue to flaking during thermal cycling. In the case of BST, one such edgering material is titanium.

The lid assembly 14 preferably comprises a main body 70 machined orotherwise formed of a metal having a high thermal conductivity, e.g.,aluminum. The main lid body defines an annular channel 74 formed aroundits perimeter to define a thin outer wall 76. A support ring 78,preferably made of stainless steel or other thermal insulator, isdisposed in the channel to provide structural support for the lid and toprevent thermal conduction to the outer wall 76. The thin outer wall ofthe body member provides a thermal choke for the base 71 of the lidwhich is sealed to the chamber body during processing at the O-ring seal72. The O-ring seal 72 is positioned at a circumferential interface ofthe chamber body 12 and the lid assembly to maintain a hermetic andvacuum tight seal of the chamber. In order to actively cool the O-ringseal, one or more cooling channels 73 are preferably disposed in thelower lip of the outer wall 76. A heat exchange fluid (e.g., water,ethylene glycol, silicone oil, etc.) circulates through the channel toremove heat at the O-ring seal.

The thermal choke provided by the thin outer wall 76 isolates the O-ringseal 72 between chamber lid assembly 14 and the chamber body 12 from theheat generated by heating elements 80 disposed in the lid. The heatchoke provides thermal protection of the O-ring seal 72 by allowinglocalized active cooling within the channel on top of the O-ring seal72, without inducing significant detrimental cooling effects on theother system components. The thin wall 76 presents an effective thermalbarrier between the heating elements and the O-ring due to its smallcross-sectional area (A) and long length (l).

The upper surface of the main lid body 70 defines a plurality of annularrecesses 79, such as spiral grooves, for receipt of a heating element 80therein. In a preferred embodiment, a heater with a power output ofabout 6200 W is used. However, the amount of power will vary dependingon the lid design and geometry, including material composition of thelid, and the process temperature. Power is delivered to the heatingelements through a feedthrough 85 disposed in the lid. The heater ispreferably controlled with conventional PID feedback control, based onsignals received from a thermocouple 82 positioned or otherwise disposedin the lid. An annular plate 84 serving as a heat shield is mounted onthe top of the heating elements. Preferably, the plate 84 is brazed tothe lid body to form an integral part of the lid body. A water cooledcover plate 86 is disposed on or over the plate 84 to provide acontrolled mechanism for pulling heat out of the lid for active feedbacktemperature control.

A cooling channel 100 is preferably formed in top cover plate 86 of thelid assembly 14. Cooling channel 100 removes heat from the lid. Inaddition, a thermal choke gap, preferably about 25 mils, is used tocontrol the amount of heat removed from the lid during cooling. Duringdeposition of a material such as BST, the substrate will be heated bythe substrate support member to a temperature of over 500° C. Heat fromthe substrate and the substrate support member will radiate onto the gasdistribution plate 26 thereby tending to increase its temperature abovethe optimum isothermal system temperature. By increasing the thermalconduction or transfer between the lid and the gas distribution plate26, the substrate and substrate support member induced temperaturegradients and fluctuations can be reduced. In order to improve heatconductivity between the lid and the gas distribution plate 26, an inertgas (e.g., helium, hydrogen, etc.) is circulated about the annularinterface of these elements. The inert gas is introduced into channel102, which may be circular, spiral or other shape, disposed in the lid.The channel can be formed in the mating annular surface(s) of the gasdistribution plate 26 and the main lid body 70 and/or in the cover plate86. The inert gas can be introduced from the top through the coolingplate or through the bottom of the chamber via a feedthrough connectedto the gas manifold. Gas pressure in the channels can be maintainedwithin the range from about 1-100 Torr, preferably within the range ofabout 1-20 Torr. Due to its high thermal conductivity, the circulatinginert gas can improve heat transfer between the lid assembly 14 and thegas distribution plate 26.

The lid assembly, including the heating element, is configured tomaintain the vapor inlet passageway and gas distribution plate at anideal isothermal system temperature, e.g., 250° C.±5°. Passive andactive cooling elements are used to maintain the top cover of the lid,and the O-ring seal 72 positioned between the chamber body and the lidassembly, at a substantially lower temperature, e.g., 100° C. or lower.

Referring again to FIG. 2, the mixing gas manifold 46 includes a centralopening 88 which delivers the gases to a blocker plate 90 to initiallydisperse or distribute the gas(es) over a large area above a face plate92. Each of the blocker plate and the face plate have a plurality ofholes formed therethrough which evenly disperse the gas over the area ofthe plates 90, 92 and together form the gas distribution plate 26. Theface plate 92 delivers the gas uniformly over the area of a substratepositioned on the substrate support member 24. The gas distributionplate 26 and the mixing gas manifold 46 are preferably made of aluminumand are sufficiently thick to allow heat transfer from the gasdistribution plate to the temperature controlled lid assembly 14.

With respect to the gas distribution plate assembly, the use of aconventional thin blocker plate 90 with a relatively thicker face plate92 also serves as a thermal control system. The mixing gas manifold 46serves as a heated mass whose heat capacity and high thermalconductivity act as a source of thermal inertia resisting temperaturevariations from the center of gas distribution plate to its periphery.The gas mixing manifold 46 also avoids the effects of gas "channeling"through the material of the plate for providing a more even distributionof gas volume across the substrate surface. While the gas distributionplate is preferably made of aluminum, another thermally conductivematerial may also be used.

FIG. 7 is a top view of a chamber lid showing the heating element 80 andthe mixing gas manifold 46. The lower surface of the lid body definesone or more channels 104 for mounting a gas manifold 46. One or moreoxidizer gas passages 52, similar to passage 38, are also formed in thechamber body 12 adjacent the passage 38 for receiving an oxidizer gasdelivery feedthrough which can be heated if desired to deliver one ormore oxidizer gases through the chamber wall to the mixing gas manifold46. A gas passage 54 is formed in the mixing gas manifold 46 to deliverthe oxidizer gas to a gas outlet 56, which provides a mixing point,located in the gas manifold adjacent the entry port into the gasdistribution plate 26. A restrictive gas passage 37 connects the end ofthe oxidizer gas passage 54 to the end of the vaporized gas passage 48to provide high velocity delivery as well as mixing of the gas mixtureupstream from the gas distribution plate 26. FIG. 8 is a partial crosssectional view of a gas manifold 46. The gas manifold 46 includes a gasdelivery block 61 which defines one or more gas passages 48, 54 thereinhaving one or more gas inlets 38, 52 on one end and a gas outlet 56 onthe other end. The gas outlet 56 serves as a gas inlet of the gasdistribution plate 26. An annular conductance restrictor plate 63 ismounted on the lower surface of the gas delivery block to mount the gasdistribution plate and prevent gas leakage at the interface between thegas manifold and the gas distribution plate. The conductance restrictorplate 63 is sized and adapted to define an annular mounting recess 65 towhich the gas distribution plate is secured.

A vaporized first gas passage 48 and an oxidizer gas passage 54 extendat least partially along the length of the gas manifold from the gasinlets to the gas outlet. The restrictive gas passage 37 is disposedbetween the vapor gas passage and the oxidizer gas passage to optimallymix and deliver the oxidizer gas into the gas outlet and then to theblocker plate and face plate. The restrictive gas passage 37 deliversthe oxidizer gas into the vaporized gas passage at a relatively highvelocity to assist in mixing of the gases. Alternatively oradditionally, a second set of a vaporized gas passage and an oxidizergas passage, a carrier gas passage or a cleaning gas passage (to delivera cleaning gas species from a remote plasma source) may also be providedthrough the chamber wall to deliver these gases to a second gasmanifold.

FIG. 4 shows a partial cross sectional view of a pumping system 18 ofthe present invention. The pumping system 18 includes a pumping nose 106mounted on the chamber which connects an exhaust passage and relatedpumps to the chamber. The pumping nose 106 includes a housing 108 whichdefines a gas passage 110 along its length. The housing supports aremovable heated liner 112. Both the housing and the liner define a pairof ports 114, 116, one port 114 connected to a cold trap and exhaustpump and the other port 116 connected to a turbopump 118, or other highvacuum pump, with a gate valve 120 disposed therebetween.

The removable heated liner 112 is shaped and sized to slidably mountwithin the nose housing 108 and includes a mounting flange 122 on oneend to mount to the end of the housing. A second mounting plate 123 ismounted on the first and sealed thereto using an O-ring seal 125. Theexhaust liner includes a body 124 which defines a central gas passage110 opening into the exhaust manifold in the chamber and the two exitports, preferably connecting a high vacuum pump and an exhaust pump andrelated cold traps. Six mounting blocks 126, 128, 130 (three of whichare shown) extend at least partially along the length of the centralpassage to mount four cartridge heaters 132 and two thermocouples 134.The multiple thermocouples provide a back up as well as enable checkingtemperature uniformity. In one embodiment, the thermocouples extendalong the bottom of the liner while the heaters are disposed along thetop and in the central portion of the liner. However, otherconfigurations such as heaters on the top and bottom and thermocouplesin the middle or heaters on the bottom and middle and thermocouples onthe top are contemplated by the present invention. The heaters arepreferably connected in parallel and two connections are provided on themounting flange of the liner for easy connection to a power source. Acap may be mounted over the mounting plates when removed from the systemso that the exhaust liner can be easily cleaned without the risk ofjeopardizing the electrical connections to the heaters. The cap can besealed to the second mounting plate 123 using an O-ring seal or othersuitable seal. Also, a handle is preferably mounted on the secondmounting plate to facilitate easy removal of the exhaust liner from thenose and submersion in a cleaning bath. Preferably, the second mountingplate 123 includes quick connects for the heaters and the thermocouplecables. FIG. 12 is a front view of the second mounting flange 122showing the heater and thermocouple connections and positions.

FIG. 11 is a cross sectional view of a removable heated liner 112. Theend of the liner adjacent mounting flange 122 includes a thin walledportion 136 around its circumference which acts as a thermal choke. Thethermal choke ensures that an O-ring disposed between the mountingflange 122 and the exhaust housing is not subjected to elevatedtemperatures. Additionally, the thermal choke regulates the amount ofheat transferred to the housing thereby minimizing (i.e., optimizing)the amount of power required to heat the liner. The end proximate thechamber is curved to match the curvilinear contour of the inner wall ofthe exhaust manifold. TEFLON® screws 138 are inserted at the chamber ofthe exhaust liner on at least the bottom and/or the sidewalls of theexhaust liner, preferably both, to provide a smooth surface on which theliner can slide on insertion into or removal from the housing to preventscratching of the nose liner and/or housing. TEFLON® is preferredbecause it can withstand 250° C. temperatures, it does not outgasunwanted contaminants and is compatible with various aggressive cleaningsolutions. However, screws or plugs formed of other materials possessingthese characteristics can be used effectively.

Referring to FIG. 4, a turbopump 118, or other high vacuum pump, ismounted to an outlet port 116 of the pumping nose. A gate valve 120 isdisposed between the turbopump and the nose to enable selectivecommunication of the turbopump with the chamber. The turbopump enablesthe vacuum chamber to be evacuated down to a very low pressure to becompatible with processing platforms such as an Endura® platformavailable from Applied Materials, Inc. of Santa Clara, Calif. An exhaustpump such as a roughing pump, dry pump or other pump used in theindustry is connected to the chamber at the exhaust port 114 in the noseto pump the chamber during processing. A cold trap 140 is disposed inthe conduit connecting the exhaust pump to filter out the depositionmaterial which may be detrimental to the pump. Additionally, a secondcold trap 142 is disposed below the first cold trap and is connected toa bypass line from the vaporizer. The bypass line and related cold trapallow the system to operate in a continuous flow made by allowingdelivery of vaporized material thereto during wafer transfer.

FIG. 13 is a perspective view of a cold trap filter of the presentinvention. The cold trap is housed in a tubular housing 144 (shown inFIG. 1) and includes a filtering member 146 which includes a pluralityof cooled passages 148 for condensation of material thereon. Thefiltering member includes a base portion 147 and a filtering portion149. The filtering portion 149 includes the plurality of cooled passages148 formed therein. A water inlet 151 and water outlet 153 are disposedin conduits 155, 157. The gases pass through the filtering member andcontinue through an exhaust passage deposed in communication with acentral portion 150 of the filtering member. This structure enablesgases to pass through the filtering portion 149 and on through theexhaust system. The housing 144 mounts a conduit connected to theexhaust pump having an inlet fluidically connected to the centralchamber portion 150 so that the gases pass through the cold trap andcontinue on through the conduit to a disposal system.

A purge gas arrangement provides a purge gas in the lower part of thechamber resulting in a gas shield with upwardly directed flow of gasemanating from the bottom of the chamber. The gas shield strength isadjustable with a mass flow controller. Suitable purge gases includehelium, argon and nitrogen, which can be introduced through a purge lineand a circular manifold for distributing the gas evenly about thesubstrate support member and the elevator shaft, within the sealingbellows. The gas flow rate must be set relatively low, e.g., 50 sccm, inorder to avoid interference with the deposition process. Additionally,the purge gas is directed into the exhaust plenum adjacent the liner andaway from the edge of the wafer.

The Vaporizer

FIG. 14 is a perspective view showing the vaporizing module 16 mountedadjacent to the chamber 12. A vaporizer 154 is mounted in a vaporizercabinet 155 and includes an outlet line 156 connected to the inlet intothe chamber. Disposed along the outlet line 156 is a first valve 157which is connected in turn to a bypass line (not shown) extending outthrough the back of the cabinet 155 and is connected to the exhaustsystem by a conduit in which the cold trap 142 is disposed (see FIG. 1).The bypass line is adapted to deliver both vaporized gas as well asliquid solvent into a cold trap disposed downstream from the valve inpreparation of delivering vaporized gas to the chamber or duringcleaning of the system. This valve controls delivery of the vaporizedmaterial to the chamber or through the cold trap in the exhaust system.A second valve 158 is disposed downstream from the first valve toselectively deliver the vaporized gas into the chamber. The second valveis mounted to the lower portion of the chamber via a rod and washerassembly 159. This assembly enables adjustment of the delivery line aswell as the valve in relation to the chamber. The mount generallyincludes first and second rings 160, 161, respectively, one disposed inthe other, to allow rotatable adjustment of an isovalve 158 and thedelivery line. The isovalve 158 is mounted to the outer ring 163 via aplurality of rods 162 (four shown here) which are mounted from the ringand include a spring 163 disposed above the upper portion of the rod andthe ring 161. The two rings 160, 161 enable rotation of the assemblywhile the spring and rod arrangement allow vertical adjustment of theassembly to ensure proper alignment of the gas feed line 156 into thechamber through the feedthrough 40, shown in FIG. 2. In general, thesuspension apparatus provides automatic compensation for thermalexpansion/contraction to maintain vacuum seals without the mechanicaland thermal stress.

FIG. 15 is a cross sectional view of one embodiment of a vaporizer 154of the present invention. The vaporizer generally includes an injectionnozzle 170 disposed through an inlet port 172 of the vaporizer. Aconcentric passage 174 is disposed about the outer perimeter of the gasinjection nozzle 170 to deliver one or more carrier gases to the tip ofthe nozzle. Preferably, the concentric gas passage is made of PTFE forlow friction coefficient and prevention of clogging. The carrier gasesare flown concentrically about the nozzle to prevent liquid dropletsfrom forming on the tip of the nozzle and moving up the outer cylinderof the nozzle. The liquid delivered to the nozzle 170 is carried in acarrier gas, such as argon, and delivered to a central cup-shapedportion 176 of the vaporizer. The cup-shaped portion of the vaporizerforms the central receptacle for the liquid injection stream wherevaporization commences. A plurality of fins 178 are disposed around thecentral cup-shaped portion 176 to define a tortuous path or labyrinthalong which vaporization occurs. The fins 178 are spaced from oneanother in rings which are offset to form the path along which the gasvapor diffuses and are spaced a sufficient distance to reduce thelikelihood of clogging. One or more notches 180 are formed in the upperportion of the fins to define a gas flow passage which allows gas flowbut which enables the fins to trap any liquid which is not vaporized.This prevents liquids from passing through the vaporizer and into thechamber, as well as enabling a solvent to be delivered into thevaporizer for cleaning without the risk of having the solvent enter thechamber.

Connected with the circular path defined between the outermost circle offins and internal cylindrical wall surrounding the vaporizer section area plurality of ports 182 (e.g., six) and associated gas deliverypassages converging to a main outlet 184. The arrangement of angledports 182 provide a large conductance for shorter resonance time in thevaporizer and also facilitate inspection and cleaning of the vapor flowpaths. All of the passages are surrounded by a large solid mass of alower block 186 and an upper block 188 which are assembled together toform the vaporizer and include a metal-to-metal seal 187. The upper andlower blocks define grooves 190 to mount heating elements. Thisarrangement helps to ensure that the vaporizing surfaces as well as thevapor are maintained at the optimum isothermal temperature downstream of(as well as in) the main vaporizing section.

The fins 178 of the vaporizing section are preferably formed as integralparts of the upper and lower block, and not as separate attached parts.Thus, in contrast to previous designs, the heating surfaces do notconstitute thermally "floating pieces," i.e., pieces whose temperature"floats" or varies (less controllably) in relation to the temperature ofone or more separate thermal masses to which the pieces are attached. Ina preferred embodiment, respective sets of fins are machined directlyinto the mating surfaces of the upper and lower blocks in complimentaryconfigurations which interleaf or interdigitate with each other to formthe multi-path, maze-like structure shown in FIG. 16. In addition totheir vaporizing function, the twists and turns of the pathways of themain vaporizing section also serve to vigorously mix the precursorcomponents and carrier gases and to filter out entrained droplets byimpaction as the carrier gas changes direction in the labyrinth.

The radial spacing between the concentrically arranged fins ispreferably about 0.5 mm (0.020"), in order to minimize the effects ofany deposits which might form. A preferred radial spacing is within therange of about 1-3 mm (0.039-0.118"), and most preferably about 2 mm. Ina preferred embodiment, the circular fins have a height of about 2-8 mmand a density of 2-6 fins per inch (measured in the radial direction).The overall inner diameter of the preferred main vaporizer section is 75mm, and 6 concentric circles are provided with a radial spacing of about2 mm. Each of the circles has four fins; the size and circumferential(end-to-end) spacings of the fins varies directly with the diameters ofthe circles. Maximum and minimum end-to-end spacings of the fins are 30mm and 2 mm, respectively, depending on carrier gas flow, thevaporization behavior of the precursors and thermal stability of theprecursors. The spacing between the fins is important to preventclogging of the vaporizer and to provide maximum surface area on whichvaporization can occur. The precursors with low volatility requirerelatively high conductance and fewer fins. Precursors with low thermalstability require relatively short resonance time and therefore highcarrier gas flow, a short flow path and fewer fins. Precursors withviolent or droplet generating boiling phenomenon require relativelyhigher numbers of fins to enhance impaction filtering of the droplets.

An important feature of the vaporizer assembly is the arrangementprovided for delivery of the liquid precursor mixture to the mainvaporizing section, and for mixing the precursor liquid with the carriergas. The mixture of liquid precursor components is delivered through thenozzle 170 or capillary tube (e.g., 2-20 mil inner diameter) to a pointjust above the center of the main vaporizing section. The liquid and gasare supplied at a relatively high flow rate, e.g., 10 ml/ min. liquidand 100-2000 sccm gas, which causes the liquid to exit the capillarytube and enter the main vaporizing section as a jet of liquid and gaswith a high nozzle velocity. Importantly, all but a final short segmentof the path of the liquid mixture is kept relatively cool by a thermalchoke structure 195 to reduce thermal decomposition of the liquidprecursor components prior to vaporization. In particular, the capillarytube extends within a relatively thin tube or neck 192 attached to orforming an integral part of the upper block as shown in FIG. 15. Thermalinsulation of the capillary tube along this stretch is provided by therelatively thin wall of the neck, e.g., 10-100 mil thickness, as well asby the space between the capillary tube and surrounding internal surfaceof the neck and by the thermal insulating value of the material. Theneck is preferably made of PTFE, stainless steel or other materialhaving a relatively low thermal conductivity. A cooling block 197 andcooling channel 199 enable temperature control of the nozzle 170.

The liquid precursor components are mixed with a concentricallydelivered carrier gas as the former is jetted-out of the capillary tubejust above the main vaporizing section. The concentrically deliveredcarrier gas is delivered to this point by a supply line 193 or tubefluidly connected, e.g., with a standard VCR fitting, with an upper partof the internal bore of the neck. The gas flows downwardly within thepassage 174 defined between the injection nozzle 170 and the internalneck surface. At the level of the nozzle outlet, the carrier gaspicks-up the liquid precursor mixture jetting-out of the capillary tubeand carries the mixture down into the main vaporizing section 176 wherethe liquid precursor is vaporized. To allow for optimization of thisinitial "flash" vaporization, the spacing between the injection tubenozzle 170 and the main vaporization section 176 is preferablyadjustable. For example, the capillary tube can be made axially movablewithin a thermal choke structure 195 mounted within the central neckbore. Adjustment of the flash vaporization to avoid a liquid droplet"dance on the frying pan" effect is obtained by adjusting the flow rateof the gas and liquid precursor mixture. Any liquid droplets remainingafter the initial "flash" vaporization are vaporized as the mixtureadvances through the tortuous paths of the main vaporizer section, incontact with the heated fins. The resultant deposition gas then passesthrough the ports and angled ports 182 to the central main outlet 184,and through the vaporizer outlet port for direct delivery to thedeposition chamber. The mixture is substantially maintained at thepredetermined optimum isothermal system temperature (e.g., 250° C.±5°).The exit ports are designed for large conductance so that precursorvapors are readily carried from the vaporizer into the chamber.

The vaporizer operates to vaporize a mixture of precursor components,such as BST, and a carrier gas by providing a main vaporizer sectionwith increased surface area provided along a tortuous pathway whichexpose the mixture to a large area of evenly heated surfaces and filterout liquid droplets entrained in the flow by droplet impaction duringchanges in gas flow direction in the tortuous path. The flow velocity,and therefore impaction filtering efficiency, is independentlycontrolled by the flow of an auxiliary argon or other carrier gas inputto he vaporizer injection plumbing. In contrast to conventionalarrangements, the amount of heating, e.g., vaporizing, power supplied tothe mixture is set substantially higher than the level of power actuallyrequired to achieve complete vaporization. The amount of power requiredfor complete vaporization is a function of the chemistry of theprecursor components and carrier gas, and the flow rate of the mixture.As one example, with a BST flow rate of 0.10 ml/min and a carrier gas,e.g., Ar, flow rate of 200-300 sccm, the amount of power necessary toheat and completely vaporize the flow is approximately 10 W. As will beunderstood, a metering valve can be used to control the amount of gasflow in direct relation to the flow rate of the liquid precursorcomponent mixture.

In accordance with the invention, the thermal power transferred to thevaporizer is set to be one to two orders of magnitude higher than the 10W required for complete vaporization of the mixture, i.e., between about100 W and 1000 W, and preferably 20-30 times higher, i.e., 200-300 W. Inthis manner, the heating power absorbed by the flowing mixture is asmall fraction of the heating power which is available. Therefore, thepower absorbed by the gas vapor presents an insignificant perturbationin relation to the available heating power, making it possible tosubstantially maintain an ideal isothermal temperature (e.g. 250° C.±5°)of the heating surfaces. In general, depending on the precursorcomponent mixture which is used, the ideal isothermal system temperaturewill be in the range of about 200-300° C.

Also, the vaporizer body is configured to help ensure the maintenance ofan isothermal temperature of the main vaporizing section. Specifically,the heating surfaces are preferably integrally formed in adjoiningsurfaces of upper and lower blocks of metal, e.g., aluminum or stainlesssteel. The blocks provide a relatively large thermal mass for retentionand transmission of thermal energy generated by one or a pair of heatingelements surrounding the blocks. In a preferred embodiment, the upperand lower blocks are provided as segments of a cylindrical rod and oneor a pair of heating elements, such as a cable heater, are wrappedhelically about the circumference, and along the lengths, of the rodsegments.

As one specific example, the top and bottom cylindrical blocks may eachhave an outer diameter of 3.5". The top segment may have a length of 1",and the bottom segment a length of 2". The segments may be boltedtogether by a plurality of bolts, e.g., eight, extending in an axialdirection and equally spaced around the perimeter of the blocks.Preferably, the segments are sealed to each other with a known type ofhigh temperature metal-to-metal seal situated in a circular grooveprovided in one or both of the blocks and surrounding the main vaporizersection. One example of a metal-to-metal seal is the aluminum Delta sealfrom Helicoflex.

The heating elements preferably deliver a total heating power of betweenabout 1000 W and 3000 W to the blocks. If separate heaters are used toheat the top and bottom segments, a 1500 W bottom heater and a 675 W topheater may be used to provide a total heating power of 2175 W. Helicalgrooves (not shown) are preferably formed on the outer surface of theblocks and the heating elements are secured in the grooves, e.g., bywelding. The heater is controlled to maintain the main vaporizingsection at the optimum isothermal temperature by a conventional PIDcontroller. The controller is connected with a thermocouple positionedwithin one, and preferably both, of the upper and lower segmentsdirectly adjacent the heated vaporizing surfaces.

In an alternative embodiment shown in FIG. 17, the upper and lower blockdo not provide interdigitating fins, but rather provide a fin structure178 is disposed only on the lower block. The upper block defines anupper roof 179 of the vaporizing chamber. The fins 178 are spaced fromone another and include passages therethrough to enable flow ofvaporized gas through the fin structure and out through the outlets. Itis believed that this arrangement enables greater conductance ofvaporized gas and to reduce resonance time in the vaporizer.

Applications Of The System

Exemplary metal-oxide layers which can be deposited using the presentsystem may include tantalum pentoxide (Ta₂ O₅), a zirconate titanate(ZrxTiy Oz), strontium titanate (SrTiO₃), barium strontium titanate(BST), lead zirconate titanate (PZT), lanthanum-doped PZT, bismuthtitanate (Bi₄ Ti₃ O₁₂), barium titanate (BaTiO₃), BST, PZT,lanthanum-doped PZT, or the like. Other materials which can be depositedinclude those materials having a narrow range between vaporization anddecomposition.

Substrates used in the present invention include primarily P-type andN-type silicon. Depending on the particular process chemistry anddesired end product, other substrate materials may be usable, includingother semiconductors, e.g., germanium, diamond, compound semiconductors,e.g., GaAs, InP, Si/Ge, SiC, and ceramics.

The selection of materials for the layers above the circuit element inan integrated circuit device depends on the device that is formed andother layers that a particular layer currently or subsequently contacts.For example, a DRAM requires a high▴permittivity capacitor, but themetal-oxide dielectric layer does not need to have ferroelectricproperties.

Devices that can be made with the present system include, but are notlimited to, 64Mbit, 256Mbit, 1Gbit and 4Gbit DRAMs.

The system also has particular application with other liquid precursorswhich are volatile as well as materials such as copper.

Liquid Delivery System

FIG. 18 is a perspective view showing a liquid delivery system 200 ofthe present invention. The liquid delivery system generally includes aliquid precursor module 202, a solvent module 204 and a vaporizer module206. In one embodiment, the liquid precursor module 202 includes twopressurized ampoules 208, 210 and a liquid delivery line 212 connectedto each ampoule. Valves are disposed along the length of the liquiddelivery lines to control flow of liquid from the ampoules to a mixingport and then into the vaporizer. Preferably, zero dead volume valves,which are described below, are used to prevent collection of precursortherein which can compromise the valves as well as negatively affectprocess stabilization and/or repeatability. The zero dead volume valvesenable rapid flushing of precursor from the lines using solvent. Solventis plumbed to the liquid delivery 212 line by line 214 to flush thesystem during maintenance. Additionally, a purge gas line is plumbed tothe liquid delivery line to rapidly purge solvent from the line so thatthe system, including the ampoules, valves and/or LFCs, can be preparedfor maintenance in ten (10) to thirty (30) minutes. The valving isdesigned so that when necessary, solvent can be introduced into theliquid delivery line upstream form the mixing port to flush the linethrough a bypass line 218 and out through a recovery system whichincludes a cold trap and exhaust manifold.

The ampoules are designed to deliver the liquid precursors at highpressure, e.g., up to 500 psi, without having to rely on high pressurepumps, i.e., no high cycle mechanical pump with rubbing parts exposed toprecursors. To provide the pressure, an inert gas such as argon ischarged into the ampoules at a pressure of about 90 psi through line220. A liquid outlet line 222 is disposed in the ampoule so that as theinert gas, e.g., argon, is delivered to the ampoule and the appropriatevalves are opened, the liquid is forced out through the outlet through asuitable valve and into the liquid delivery line.

The liquid delivery line 212 is connected from each ampoule to thevaporizer. A first zero dead volume valve is disposed on the outlet ofthe ampoule to control delivery of the liquid to the delivery line 212.The valve is preferably a three-way valve connecting the bypass line 218and the liquid delivery line 212. The bypass line 218 in turn isconnected to a cold trap and an exhaust manifold (not shown). A highpressure gauge 224 and a LFC 226 are disposed downstream from a valve228 introducing the solvent and the purge gas. The LFC controls deliveryof the liquid to the mixing port 230 connected between the liquidprecursor delivery lines. A low pressure gauge 232 is disposed on thebypass line 218 to monitor pressure in the line so that completion ofthe maintenance routine can be determined.

The liquid precursor delivery lines 212 deliver liquid precursors intothe mixing port 230 upstream from the vaporizer 154. A solvent deliveryline 234 also delivers a solvent into the liquid delivery linedownstream from the mixing port where the liquid precursors and thesolvent are mixed and delivered into the vaporizer. At the vaporizer, acarrier gas line 236 delivers a carrier gas into the delivery line tocarry the liquid precursors and the solvent into the vaporizer throughthe capillary tube or nozzle. In addition, a concentric carrier gas line238 delivers a carrier gas around the nozzle or injection tip to ensurethat even a small amount of liquid is delivered to the vaporizingsurfaces. The delivery line from the mixing port and into the vaporizeris preferably made of a material having a low coefficient of friction,such as TEFLON® PTFE, and does not hang up in the line. This featureassists in the delivery of small volumes of liquid precursor.

The solvent module 204 includes one or more chargeable ampoules similarto the liquid precursor ampoules. Preferably, there are two solventampoules 240, 242 and two liquid precursor ampoules 208, 210. The liquidprecursor ampoules can deliver two separate precursors which can bemixed at the mixing port or can deliver the same precursor together oralternatively.

The liquid precursor ampoules are designed with a slotted/sculpturedbottom to draw the liquid downwardly in the ampule so that the liquidmay (1) be detected at very low levels and (2) be drawn out of theampule even at low levels. This is particularly important in dealingwith expensive liquids which are preferably not wasted. In addition, theampoules include an ultrasonic detector for discerning the volume ofliquid in the ampoule even at low levels so that continuous processingmay be achieved.

FIG. 19 is a perspective view of a zero dead volume valve. The valveincludes a liquid precursor inlet 252 and a solvent inlet 254 and asingle outlet 256. The solvent is routed through the solvent inletthrough a solvent control actuator 258 and into the liquid precursorcontrol actuator 260. A plunger 262 controls entry of the solvent intoand consequently out of the solvent control actuator as shown in FIG.20. The liquid precursor is routed through the precursor inlet 252 andinto precursor control actuator 260 when the plunger 264 in the actuatoris in the open position. When the plunger is in the closed position, theprecursor is prevented from entering the actuator and is flushed out ofthe valve by the plunger and by flow of solvent through the valve. Thesolvent is able to enter the precursor control actuator 260 whether theplunger is in the open or closed position to enable solvent purge of thevalve as shown in FIG. 20. The plunger is contoured to seal the liquidprecursor inlet while enabling solvent flow into the actuator.Continuous solvent flow allows the system to be continuously purged withsolvent when the liquid precursors are shut off.

Additionally, a single actuator valve is disposed on the outlets of theampules to control delivery of liquid precursor and to prevent cloggingin the actuator. Also, the two way valves are preferably disposed on thedownstream side of the liquid flow controllers in the vaporizer panel.

The delivery tubes are preferably made of a material such as TEFLON® topromote frictionless fluid flow therein to prevent clogging anddeposition along the path of the tubes. It has been learned that TEFLON®provides a better conduit for materials such as the barium, strontiumand titanium precursor liquids used in the deposition of BST.

The plumbing system is designed to enable rapid flushing of the linesand valves during routine maintenance. Additionally, the system isadapted to enable sequential shutdown of each of the valves as well asto deliver an automatic flush of a controlled amount of solvent throughthe vaporizer and the delivery lines in case of a power outage. Thissafety feature ensures that during uncontrolled power outages, thesystem will not be subject to clogging.

The delivery system may also comprise a bubbler system where a carriergas such as argon can be bubbled through a solvent to suppress prematuresolvent evaporation from the precursor, thereby ensuring the precursorliquid will not be dried out en route to the vaporizer.

In situ liquid flow controllers and pisoelectric control valves are alsoused to maintain heightened control over the system. The high pressuregauges present on precursor and solvent lines as well as vacuum gaugeson the vacuum manifolds are used to measure whether chemicals remain inthe lines. These gauges are also used for on board leak integritymeasurements.

A preferred embodiment of the present invention includes a liquid CVDcomponent delivery system having two pressurized ampoules of liquid CVDcomponent and a related LFC, such as a needle valve, which operateswithout sliding seals and can be used at pressures of less than 250 psi.Two solvent ampoules deliver solvent into the liquid delivery lines forcleaning and maintenance as well as into the mixing port duringprocessing.

BST Process

The vapor desired for use in the deposition process is shown as a mix offirst and second vaporized liquid precursors combined in predeterminedmass or molar proportions. For use in deposition of BST, the firstliquid precursor is preferably one of a mixture of Ba and Sr polyaminecompounds in a suitable solvent such as butyl acetate. The preferredmixtures combine bis(tetra methyl heptandionate) barium penta methyldiethylene triamine, commonly known as Ba PMDET (tmhd)₂, and bis(tetramethyl heptandionate) strontium penta methyl diethylene triamine,commonly known as Sr PMDET (tmhd)₂, or, in the alternative, bis(tetramethyl heptandionate) barium tetraglyme, commonly known as Ba (tmhd)₂tetraglyme, and bis(tetra methyl heptandionate) strontium tetraglyme,commonly known as Sr (tmhd)₂ tetraglyme. The second liquid precursor ispreferably bis(tetra methyl heptandionate) bis isopropanide titanium,commonly known as Ti (I-pr-o)(tmhd)₂, or other titanium metal organicsources, such as Ti(tBuO)₂ (tmhd)₂. The molar ratio between the combinedmetals in the first liquid precursor and the second liquid precursor ispreferably about 2:1:4 Ba:Sr:Ti. The molar ratio can vary from about2:1:2 to about 2:1:8.

The BST process mixes the vaporized first and second liquid precursorswith an oxidizing gas such as oxygen, N₂ O, O₃ or combinations thereof,at a temperature above the vaporization temperature of the precursorsand below a temperature which degrades the components. The process isvery sensitive to changes in temperature of the substrate, solventcontent of the liquid precursors, and concentration of the oxidizer inthe combined gases. Increasing the wafer temperature increases thedeposition rate, reducing the solvent content of the liquid precursorsreduces the haze of the films, and controlling the oxidizer flow ratecontrols the roughness of the film and crystalline phase.

FIG. 21 is a graph of the deposition rate versus heater temperature in aCVD BST 200 mm substrate process of a preferred embodiment of thepresent invention. A heater temperature of 600° C. provides a highdeposition rate without substantial degradation of the precursors. Theheater temperature can vary from about 300° C. to about 800° C. For theexamples shown in FIG. 21, the first precursor was a mixture of Ba PMDET(tmhd)₂ and Sr PMDET (tmhd)₂ in butyl acetate having a molar ratio ofBa:Sr of 2:1. The second precursor was Ti (I-pr-o) (tmhd)₂ in butylacetate which provides a molar ratio of Ba:Sr:Ti of 2:1:4. The substratewas a Pt/SiO₂ /Si substrate. A deposition rate of 220 Å/minute wasachieved at a heater temperature of 600° C. using a total liquid flowrate of the precursors at 200 mg/m and a process gas flow rate of 1500sccm (that is, a combination of oxygen, nitrogen and argon, each at aflow rate of 500 sccm). A vaporizer according to the present inventionwas also used, wherein the vaporizer lines for the precursors weremaintained at 240° C.

As shown by FIG. 21, the deposition rate increases an average of 1.3Å/min for each 1° C. increase in the heater temperature, showing thatthere is a strong sensitivity to temperature. A deposition rate of over200 Å/minute indicates high vaporizer efficiency.

A high deposition rate of 150 Å/minute process can provide a highquality film having good uniformity within the wafer and from wafer towafer. A heater temperature of 550° C. provided a wafer temperature of470° C. and a deposition rate of 160 Å/minute. Satisfactory electricalproperties have been obtained with a deposition rate as high as 169Å/minute.

FIG. 22 is a graph of the log of the deposition rate shown in FIG. 21versus 1 divided by the temperature of the wafer heater in 1000° K. Asshown in FIG. 22, there are two distinct regimes with respect to thedeposition rate. Mass transport of the precursors limits the depositionprocess were the log of the deposition rate is around 5 or greater. Thedeposition process is surface reaction limited where the log of thedeposition rate is about 4 or smaller. The transition between these tworegimes takes place at about 550° C., or about a 470° C. watertemperature. A 500-550° C. regime provides good uniformity for stepcoverage optimization. Results were obtained by simply varying thetemperature and observing the deposition rate. The significance is thatthe PMDETA precursors are permitting high decomposition rates and a wellbehaved reaction mechanism with a simple single transition in ratecontrolling reaction at a 470° C. wafer temperature.

FIG. 23 demonstrates the high quality films produced by this inventionusing the process conditions described for FIG. 21. Three depositionruns were made over a two day period to deposit films having thicknessesof 1150 Å, 550 Å, and 550 Å. The uniformity of the wafers is shown by agraph of measured titanium concentration (mole/%) versus wafer number aswell as measured deposition rate (Å/min) versus wafer number. This graphshows that wafer-to-wafer deposition rates are uniform and meet thedesired target rate. This graph also illustrates a rapid change in Ticoncentration for the first several wafers in each run which presents anopportunity for improvement of the process. This graph further showsthat the composition is not very sensitive to deposition time as hadbeen expected. FIG. 23 shows reasonably tight process control which canbe further improved through the use of 3-part barium, strontium andtitanium mixtures and by running the vaporizer in continuous flow mode.

FIG. 24 is a table of a Ti sensitivity test with a wafer heatertemperature of plus or minus 0.5° C. during deposition. This figureshows the mole % for Ti, Ba, and Sr for two separate wafers. Si Primemeans non-previously used silicon. Si Recl means reclaimed silicon fromother processes. Pt/ox 1 is an oxidized silicon substrate with platinumsputtered thereon using physical vapor deposition techniques. Pt/ox 2 isan oxidized platinum substrate further characterized as electron beamplatinum. The matrix results show that plus or minus 0.5° C. duringdeposition yields the best repeatability in 5 out of six cases. Inaddition, the matrix results show that the substrate is coated withabout 8-10 mole % more Ti on Pt versus Si, and about 2 mole % Ti for 20%Ti(I-pr-O) demonstrating substrate sensitivity.

FIG. 25 is a graph of the composition sensitivity of Ti, Ba and Sr totemperature in the CVD BST process described for FIG. 21, whereconcentration (mole %) of Ti, Ba and Sr are each plotted versus waferheater temperature. At about 600° C., the Ti concentration of thedeposited film increases 1 mole % for each increase in heatertemperature of 2° C. At about 600° C., the Ba concentration of thedeposited film decreases 1 mole % for each increase in heatertemperature of 2.5° C. At about 600° C., the Sr concentration of thedeposited film decreases 1 mole % for each increase in heatertemperature of 10° C. demonstrating strong temperature dependence. Thistemperature dependence is substantially reduced at a 680° C. heatertemperature.

In the preferred embodiment of the present invention, it is critical tomaintain the heater in the 600-750° C. range to optimize electricalproperties and for optimal step coverage. It has been found that certainchemicals used in a certain temperature range produce good results.Specifically, polyamine based Ba and Sr precursors and Ti (I-pr-o) arethe precursors that are believed to work the best in the presentinvention. A wafer control of plus or minus 0.50° C. is preferred forthe above-mentioned precursors.

EXAMPLE 1

A preferred process according to the present invention deposits a BSTfilm on a 200 mm wafer mounted on a heated substrate holder spaced 550mils from a gas distribution showerhead or face plate. The depositionoccurs at 1.7 Torr with a wafer temperature of 600° C. and the followingflow rates. The first precursor was 33 mg/min to 200 mg/min of a mixtureof Ba PMDET (tmhd)₂ and Sr PMDET (tmhd)₂ in butyl acetate having a molarratio of Ba:Sr of 2:1. The second precursor was 17 mg/min to 77 mg/minof Ti (I-pr-o) (tmhd)₂ in butyl acetate which provides a molar ratio ofBa:Sr:Ti of 2:1:4. The substrate was a Pt/SiO₂ /Si. A deposition rate of40 to 160 Å/minute is achieved using process gas flow rate of 2900 sccm(that is, a combination of O₂ at 500 sccm, N₂ O at 500 sccm, Ar_(A) at1500 sccm, and Ar_(B) at approximately 900 sccm). A vaporizer accordingto the present invention was also used, wherein the vaporizer lines forthe precursors were maintained at 240° C.

EXAMPLE 2

In another example, a process according to the present inventiondeposits a BST film on a 200 mm wafer mounted on a heated substrateholder spaced 550 mils from a gas distribution showerhead. Thedeposition occurs at 7 Torr with a heater temperature of about 680° C.and the following flow rates. The first precursor was 33 mg/min to 200mg/min of a mixture of Ba PMDET (tmhd)₂ and Sr PMDET (tmhd)₂ in butylacetate having a molar ratio of Ba:Sr of 2:1. The second precursor was17 mg/min to 77 mg/min of Ti (I-pr-o) (tnhd)₂ in butyl acetate whichprovides a molar ratio of Ba:Sr:Ti of 2:1:4. The substrate was a Pt/SiO₂/Si. A deposition rate of 151 Å/minute was achieved using process gasflow rate of 1300 sccm (that is, a combination of O₂ at 250 sccm, N₂ Oat 250 sccm, Ar_(A) at 500 sccm, and Ar_(B) at approximately 300 sccm).A vaporizer according to the present invention was also used, whereinthe vaporizer lines for the precursors were maintained at 240° C. Asshown in FIGS. 26 and 27, a two mixture process showed repeatableresults over a twenty five wafer run.

EXAMPLE 3

In another example, the system was cleaned using acetone as a solvent.The acetone used was not dried. A deposition process according to thatdescribed in Example 1 was then performed. A 2× increase in thedeposition rate was observed indicating that residual acetone solventstabilized the precursors on delivery to the substrate and consequentlyresulted in the higher deposition rate. It is believed that the acetonestabilizes the precursors through hydrogen bonding so that moreprecursor is delivered to the substrate surface for reaction.

EXAMPLE 4

It is believed that use of a solvent such as acetone during thedeposition process will stabilize the precursors and result in a higherdeposition rate.

While the foregoing is directed to a preferred embodiment of theinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims which follow.

What is claimed is:
 1. A processing chamber lid, comprising:a) athermally conductive main body having a circumferential heat limitingchannel formed therein and adjacent to an upper surface thereof, andhaving a chamber mounting surface disposed on an outer wall disposedoutwardly from the heat limiting channel; b) a heat limiting supportmember disposed in the channel; and c) a gas distribution assemblycomprising one or more heat transfer channels formed therein anddisposed on a lower surface of the main body.
 2. The lid of claim 1wherein the gas distribution assembly comprises:a) a gas manifolddisposed on the main body, the gas manifold defining one or more gaspassages therein; and b) a gas distribution plate connected to the gasmanifold, the gas distribution plate having a first and a second gasdistributing surface.
 3. The lid of claim 2 wherein the gas manifoldcomprises a first and a second gas passage and the first and the secondgas passages are connected by a restrictive passage disposedtherebetween proximal one end thereof.
 4. The lid of claim 3 wherein thelid further comprises a heating element disposed on the main body. 5.The lid of claim 4 wherein the lid further comprises a cover platedisposed on the main body.
 6. The lid of claim 5 wherein the cover platefurther comprises one or more heat transfer channels disposed therein.7. The lid of claim 1 further comprising a vaporizer disposed on themain body and connected to the gas distribution assembly.
 8. The lid ofclaim 7 wherein the gas distribution assembly comprises a gasdistribution plate having an inlet and a first and a second gasdistributing surface.
 9. The lid of claim 8 wherein the lid furthercomprises a heating element disposed on the main body.
 10. The lid ofclaim 9 wherein the lid further comprises a cover plate disposed on themain body.
 11. The lid of claim 6 further comprising a thermocoupledisposed therein and positioned adjacent to the gas manifold.
 12. Thelid of claim 10 further comprising a thermocouple disposed therein andpositioned adjacent to the gas manifold.
 13. The lid of claim 6 furthercomprising a heat transfer channel disposed adjacent the chambermounting surface.
 14. The lid of claim 10 further comprising a heattransfer channel disposed adjacent the chamber mounting surface.
 15. Thelid of claim 2 wherein the gas manifold further comprises a conductanceguide disposed on the lower portion of the gas manifold which mounts thegas distribution plate.
 16. The lid of claim 15 wherein the conductanceguide forms a seal with the gas distribution plate to prevent gases fromflowing therebetween.
 17. The lid of claim 16 wherein the gas manifoldcomprises a first and a second gas passage and the first and the secondgas passages are connected by a restrictive passage disposedtherebetween proximal one end thereof.
 18. The lid of claim 17 whereinthe gas distribution plate further comprises one or more heat transferchannels formed therein.
 19. The lid of claim 18 wherein the lid furthercomprises a heating element disposed on the main body.
 20. The lid ofclaim 19 wherein the lid further comprises a cover plate disposed on themain body.
 21. The lid of claim 1, wherein the heat limiting member iselectrically conductive.
 22. The lid of claim 1, wherein the outer wallis at least partially separated from the channel by a thermallyresistive medium.
 23. The lid of claim 22, wherein the thermallyresistive medium comprises a gas.
 24. A processing chamber lid,comprising:a) a thermally conductive main body having a circumferentialheat limiting channel formed therein and adjacent to an upper surfacethereof; b) a heating element connected to the main body, c) a heatlimiting support member disposed in the channel; and d) a gasdistribution assembly comprising one or more heat transfer channelsformed therein and disposed on a lower surface of on the rna body. 25.The lid of claim 24, wherein the lid comprises a thermal choke.
 26. Thelid of claim 25, wherein the thermal choke is disposed on a cooler sideof the heat limiting support member away from the heating element. 27.The lid of claim 24, wherein the heat limiting support member iselectrically conductive.
 28. The lid of claim 24, wherein the outer wallis at least partially separated from the channel by a thermallyresistive medium.
 29. The lid of claim 28, wherein the thermallyresistive medium comprises a gas.
 30. The lid of claim 25, furthercomprising one or more resilient seals coupled to a cooler portion ofthe lid away from the heating element with the thermal choke disposedtherebetween.
 31. The lid of claim 25, wherein the thermal choke isintegral with the lid.
 32. The lid of claim 24, wherein the gasdistribution assembly is heated by the heating element connected to themain body.